Performance of NiO Doped on Alkaline Sludge from Waste Photovoltaic Industries for Catalytic Dry Reforming of Methane

Performance of NiO Doped on Alkaline Sludge from Waste Photovoltaic Industries for Catalytic Dry Reforming of Methane | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Performance of NiO Doped on Alkaline Sludge from Waste Photovoltaic Industries for Catalytic Dry Reforming of Methane MOHD RAZALI SHAMSUDDIN, Siow Hwa Teo, Tengku Sharifah Marliza Tengku Azmi, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3869773/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 18 Apr, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted 6 You are reading this latest preprint version Abstract Alkali sludge (AS) is abundantly waste generated from solar PV solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad 2016 ). This paper investigated alkaline sludge containing 3CaO-2SiO 2 doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was carried out to prepare the xNiO/AS (x = 5–15%) catalysts and tested them to determine their physicochemical properties. The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor/GC-TCD at a CH 4 : CO 2 flow rate of 30 ml − 1 during a 10h reaction by following (Shamsuddin et al. 2021c ). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900°C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5g), and GHSV (3000, 6000, 9000, 12000, and 15000h − 1 ) were evaluated. The results showed that while physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion and chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion results in higher reactant conversion. The catalytic performance on various parameters shows 15%NiO/AS exhibits high reactant conversion up to 98% and 40–60% product selectivity in 700 o C, 0.2g catalyst loading, and 12000h − 1 GHSV (see Fig. 1). According to spent catalyst analyses, the catalyst is stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation. Nickel alkaline sludge dry reforming methane carbon dioxide hydrogen Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Alkaline sludge from wastewater treatment facilities in photovoltaic solar cell industries is a byproduct or waste material formed during the treatment of wastewater generated during the manufacturing operations of solar cells. Multiple stages of manufacturing in the photovoltaic (PV) solar cell industry, including cleaning, etching, chemical processing, and washing, can result in the development of wastewater containing different pollutants, chemicals, and particles. Alkaline sludge is the solid residue or slurry that emerges after treating wastewater with alkaline chemicals such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). In the wastewater treatment process, these alkaline materials are utilized to precipitate or coagulate heavy metals and other contaminants present in the wastewater as well as to neutralize acidic components. Supports were critical in improving catalytic activity and reducing carbon deposition during methane dry reforming (Bradford and Vannice 1999 ). The fundamental supports used in dry reforming aided in the gasification of carbonaceous species, which reduced carbon deposition and prevented sintering (Lucrédio et al. 2011 ). Recent research on NiO-based catalysts used in DRM revealed a significant improvement in the catalytic system, particularly in reducing carbon growth by combining nickel particles together with basic metal oxide MgO and CaO (Sun et al. 2020 ) or incorporating SiO 2 (Wysocka et al. 2019 ). Support with high oxygen mobility and a strong Lewis basicity (Aramouni et al. 2017 ) might be used to enhance resistance toward coke deposition. Dry reforming of methane (DRM) reaction is one of the best solutions in realizing this approach due to not only reduced CH 4 and CO 2 emissions to the environment, but it also produces more valuable H 2 as alternative energy which is cleaner and higher efficiency (Anaya et al. 2023 ). Several constraints that would hinder the efficiency of DRM reaction in producing H 2 can be overcome by implementing excellent catalysts to the reaction. The NiO-based catalyst could be the better choice which is more economical compared to noble metal. Some improvements that hindered the reactivity and stability of NiO-based catalysts can be implemented such as introducing the basic element of Ca and/or Mg as support material. Therefore, this paper aims the utilization of low-coast material like AS will be contributed to the basic sites of the catalyst which enhanced catalytic activity and stability. The synergistic effect between effective NiO-based catalysts on DRM reaction together with the availability of basic sites in AS support materials will undergo higher catalytic performance on that reaction. Thus, application AS not only provides basic sites for the prepared catalyst but also shows the feasibility of these mineral and waste materials implemented in the catalytic reaction. Materials and Method Materials The chemicals used in the preparation of catalysts are Ni (NO 3 ) 2 .6H 2 O (ACROS with a purity of 99.8%) and AS. The AS resources for this study come from PV solar cell factory effluent in Bintulu, Malaysia. The elemental composition of AS was validated by XRF and was dominated by SiO 2 (61.93%), CaO (31.78%), Fe 2 O 3 (2.00%), Na 2 O(1.5%), Cl (1.18%), and Al 2 O 3 (0.41%). Linde Malaysia Sdn. Bhd. supplied the reactant gas, which comprises high quality CH 4 and CO 2 at a concentration of CH 4 :CO 2 : = 50:50 vol.%. Catalyst preparation Prior to catalyst production, AS tended to be calcined at 900°C in an air environment. The impregnation technique was used to prepare NiO-supported AS with various Ni loadings and dispersed in distilled water. In order to achieve a homogeneous solution of prepared [x]NiO/talc (x = 5, 10, 15 wt%), a complimentary quantity of AS and an adequate quantity of Ni salt were incorporated in 100 mL of distillate water and constantly stirred. The mixtures were then gently heated at 150°C to remove any remaining water before drying overnight at 100°C. The dried precursors were crushed into a fine powder and calcined at 600°C for 3 hours at a heating rate of 10°C min − 1 in the air atmosphere. Catalyst characterization The N 2 adsorption-desorption study was carried out at -196°C utilizing a Micromeritic ASAP2020 to quantify BET surface area, pore volume, and size. The sample was degassed at 150°C for 8 hours before identification to remove any water or other adsorbed gas from the catalyst surface. X-ray diffraction (XRD) (PANalytical X'Pert Pro-MPD diffractometer) coupled with a solid-state detector was used to determine the phase composition and the crystallite properties of catalysts. To identify the crystal phases of the produced catalyst, the results were recorded at 2θ between 5° and 80° with a scan speed of 4°min − 1 . In preparation for pre-treatment, 0.05 g catalysts were placed into the quartz tube reactor (ID = 6 mm) and treated for 10 minutes at 150°C under N 2 gas flow (20 mL min − 1 ). The procedure was conducted with a 5% H 2 /Ar flow rate of 25 mL min − 1 from room temperature to 950°C with a heating ramp of 10°C min − 1 . A field emission scanning electron microscope (FESEM; JEOL JSM-7600F) combined with an energy dispersive X-ray detector (Oxford INCA X-MAC 51 XMX 0021) was used to analyze the morphology and elemental content. Catalytic performance The catalytic activities of the DRM reaction over NiO/AS were evaluated in a fixed bed stainless steel microreactor combined with a GC system (ID = 6 mm) for 3 hours at varied temperatures (600 to 800°C) and reactant concentrations of CH 4 :CO 2 : = 50:50 vol.%. The gas product was identified using an Agilent 6890 N (G 1540 N) online gas chromatograph equipped with Varian capillary columns HP-PLOT/Q and HP-MOLSIV. The GC directly detected all gaseous concentrations in both the inlet and outlet streams. The equations were used to calculate CH 4 and CO 2 conversion (xCH 4 & xCO 2 ) with H 2 and CO selectivity (SH 2 & SCO) as described by (Shamsuddin et al. 2021c ). Results and Discussion Textural properties The DRM catalytic performance is affected by the textural properties of the catalyst. As a result, Fig. 1 depicts textural qualities in terms of surface area and porosity (N 2 adsorption-desorption) as well as crystal phase (XRD). The N 2 adsorption-desorption isotherm of NiO/AS catalysts was depicted in Fig. 1 A. All of the catalysts exhibit a type III isotherm with an H3 hysteresis loop. This shows that all NiO/AS catalysts are nonporous or macroporous solids with weak adsorbent-adsorbate interactions (Thommes et al. 2015 ). Thus, the H3 form of the hysteresis loop reveals that these macroporous solids are made up of pore networks that are only partially filled with pore condensate (Thommes et al. 2015 ). However, nickel impregnation boosted the produced catalysts' ability to adsorb, while also increasing BET surface area, S BET ; pore size, and pore volume (see Table 1 ). The following orders caused an increase in pore volume and SBET: 15% NiO/AS, 10% NiO/AS, and 5% NiO/AS It was discovered that increasing the NiO loading lowered S BET and pore volume due to pore obstruction by NiO particles (Shamsuddin et al. 2021a ). Compared to 5%NiO/AS and 15%NiO/AS, 10%NiO/AS had the largest pore size because it formed larger pores (5–50 nm). The pore size distribution of xNiO/AS catalysts is shown in Fig. 1 B as bimodular porosity with small mesopore (4nm) and wide mesopore (5–50 nm) (Groen et al. 2003 ). Furthermore, when compared to others, 15%NiO/AS (refer to Fig. 1 B*) has the largest distribution of narrow mesopore type. This demonstrates that metal addition displayed good sustentation of catalyst porosity (Kaydouh et al. 2015 ). The phase composition of crystallized NiO/AS catalysts was shown in Fig. 1 C. All AS-supported catalysts produce SiO (JCPDS 01-0378) and 3CaO.2SiO 2 (JCPDS 02-0323). The intensity peaks of NiO (ICDD 00-022-1189) correspond to the planes of cubic NiO species and grow as NiO loading increases at 2θ (h,k,l) = 37°(111), 43°(200), 62°(220), 75°(311), and 79°(222). Thus, the creation of intermetallic CaNi 5 (JCPDS 19–0244) demonstrates a significant interaction between active metal (Nickel) and support (Penner and Armbrüster 2015 ). Additionally, NiO crystallite sizes (see Table 1 ) obtained using the Debye-Scherrer equation at 2θ = 43° show that NiO/AS catalysts grew in the following orders: 5% NiO/AS, 15% NiO/AS, and 10% NiO/AS. As a result, Table 1 reveals that 15%NiO/AS has the most extensive NiO dispersion percentages when compared to 5%NiO/AS and 10%NiO/AS. In contrast to 15%NiO/AS, 10%NiO/AS showed a somewhat greater intensity of intermetallic CaNi 5 , which resulted in a lesser dispersion of NiO. In essence, the development of narrow mesopore types leads to an improvement in the size of the NiO crystallized phase and an increase in catalyst NiO dispersion. Table 1 Physicochemical properties of NiO/AS catalysts Properties S BET (m 2 g − 1 ) Pore Size (nm) Pore Volume (cm 3 g − 1 ) NiO Crystallite size (nm)* NiO Dispersions (%)** TPR-H 2 TPD-CO 2 Catalysts Temp (℃) Amount (µmolg − 1 ) Temp (℃) Amount (µmolg − 1 ) AS 4.99 15.33 0.0065 n/a n/a n/a n/a 571 851 109.72 6.32 5%NiO/AS 15.84 15.31 0.0349 39.49 22.4 403 601 198.32 1709.74 307 693 26.88 133.56 10%NiO/AS 13.21 25.30 0.0345 66.98 37.9 439 603 267.14 2562.45 402 693 824 207.59 317.29 107.48 15%NiO/AS 12.60 17.28 0.0282 47.73 42.2 425 519 1547.82 2045.53 399 723 784 18.41 154.61 35.74 * derived from Debye-Scherrer equation obtained by NiO peaks at 2θ = 43° ** derived from H 2 -TPR results as suggested by Fadoni et al. (1999). Surface morphology by FESEM-EDX The xNiO/AS catalyst's surface morphological characteristics have been examined to ascertain the impact of the surface structure on the physicochemical properties of the developed catalyst. In accordance with Fig. 2 , the images retrieved from the AS support (Fig. 2 A) showed a coral-like formation with several brunches all around the catalyst. It's interesting to note that the produced image displays hierarchical units attached together to form a coral shape made up of a number of aggregates resembling dendrites. As the quantity of NiO loading on support increases, it is added gradually to AS modifications. Images of a 5%NiO/AS catalyst in Fig. 2 B demonstrate very minor alterations to the catalyst's structural integrity. Images at higher magnification show the development of nodules at a specific location on the surface of the catalysts. These nodules' presence is evidence that AS's surface was effectively impregnated with NiO. This impregnation is therefore demonstrated by an elevated plot level (approximately 5%) of EDX. The surface morphology of the catalyst is significantly altered when the NiO loading is increased by 10% (Fig. 2 C). A towel-like structure has formed on the catalyst's surface subsequent to the coral-like structure collapsing. Apart from that, larger NiO particles started to emerge between the AS structure's gaps. Numerous nodule particles (grainy-like) were scattered on these towel-like structures as a result of higher impregnation of NiO up to 15%. A high-magnification image demonstrates evenly distributed rough particles, supporting the conclusion of the NiO dispersion degree (Table 1 ). As a result, these exceptional qualities are anticipated to enhance DRM catalytic performance. Reduction behavior To explore reduction behaviors, the estimated oxygen storage capacity of each metal oxide was measured using the TPR-H 2 analysis (Samsuri et al. 2020 ). The reducibility. The reducibility of active metals is crucial in the DRM reaction because it offers vacancy active sides, which oxygen abandons throughout the reduction process (Puigdollers et al. 2017 ). According to TPR-H 2 analysis conditions, Fig. 3 a depicts the reduction behavior of NiO/AS catalysts. The flat line on the TPR-H 2 spectra indicates that, as would be anticipated, oxides like SiO 2 and CaO in AS support were not reducible (Puigdollers et al. 2017 ). Significantly distinct peaks are produced when nickel is impregnated into an AS support, and these peaks correlate to the reduction behavior of NiO species on catalysts. Most NiO/AS catalysts displayed two dominating peaks, each of which indicated two reduction processes. The first notable peak occurs between 300 o C and 450 o C owing to the reduction of Ni 2+ to Ni 0 species on the surface of catalysts (Shamsuddin et al. 2021b ). Evidently, 15%NiO/AS exhibits the maximum quantity and intensity (see Fig. 3 a) at lower temperatures when compared to 5%NiO/AS and 10%NiO/AS. Metal-support interaction has been found to be substantially linked with catalyst reducibility. At lower temperatures, a decreased peak was created by weak contact between NiO and the AS support. However, significant interaction results in a greater temperature peak decrease. The above finding is consistent with(Lokteva and Golubina ( 2019 ) that lower metal loading would result in less metal-support interaction. Additionally, the larger dispersion of NiO species in catalyst surfaces also had an impact on the low reduction temperature. As NiO loadings were increased, the percentages of dispersion of NiO in produced NiO/AS catalysts increased. Furthermore, the lowest peak intensity of 10%NiO/AS indicates that the NiO species in this catalyst is in a bulky form (largest NiO crystallite size), which is harder to reduce and may interfere with the catalyst's catalytic behaviours. As a result, the size of the crystallites increases in the following order: 5% NiO/AS, 15% NiO/AS, and 10% NiO/AS. According to (Soled et al. 2003 ), the strong association of metal to support makes it more difficult to decrease than related bulk metal oxides(Soled et al. 2003 ). Consequently, greater reduction temperatures must be achieved to provide an active metal phase, resulting in poor metal dispersion. In contrast, poor metal-support interactions result in outstanding metal oxide dispersion and decreased crystallite size, resulting in reductions at lower temperatures (Soled et al. 2003 ). Therefore, an appropriate compromise between the support and the precursor could be reached by optimal metal loading, which improved metal oxide dispersion, crystallite size, and reducibility behaviors. The subsequent findings (Fig. 3 B) were obtained by XRD scanning of reduced-xNiO/AS catalysts under the same conditions. The comparative investigation of NiO/AS with reduced-xNiO/AS catalysts reveals the production of new metallic Ni (ICDD 01-087-0712) phases at 2θ = 44.5° (111), 51.8 (200), and 76.4 (220), which greatly obliterate the NiO phase in the diffractogram. SiO 2 (ICDD 01-0378), 3CaO.2SiO 2 (ICDD 02-0323), and CaNi5 (ICDD 19–0244) phases all show significant modifications. The peak intensities of 3CaO.2SiO 2 and CaNi 5 were slightly less intense than those of the SiO 2 peaks due to the high-temperature impact observed during TPR-H 2 analysis compared to the NiO/AS catalyst. It has been established that ranging materials' response to temperature affected the change of lattice parameters and the decomposed (Shen et al. 2018 ). Basic sites properties The core of the catalytic DRM process is initiated by acid-base interactions and is sustained by reaction cycles. Particularly, CO 2 reagents are strong acidic molecules and only interact with the catalyst with basic sites. Precisely as a result, basic sites play an essential part in enhancing acidic CO 2 activation, inhibiting carbon formation on active sites, and enhancing catalytic durability [19]. TPD-CO 2 may therefore be used to evaluate these basic sites and their unique characteristics in both quantities and qualitatively. Corresponding to the CO 2 desorption temperature, Fig. 4 showed three types of basic strength, which were weak (250°C), medium (250–500°C), and strong (> 500°C) (Lahuri et al. 2017 ). The strongest basic sites are typically found at temperatures of 571°C and 851°C, by AS support. The formation of CO 2 ligands such as monodentate, bidentate, polydentate, and bicarbonate species between the CO 2 reactant and CaO basic sites matched these strong basic sites [9]. The availability of CaO as a basic site is less abundant than SiO 2 , which results in a somewhat decreased CO 2 adsorption capacity in this support (see Table 1 ). Consequently, XRD analysis demonstrated that the production of intermediate species of 3CaO.2SiO 2 reduced the creation of CO 2 ligands. In comparison to AS support, the TPD-CO 2 profiles of xNiO/AS catalysts exhibit substantial variations due to the resulting formation of moderate basic sites and peak shifting of strong basic sites. The presence of free O 2− anions from the NiO species, which are provided by surface defects on the catalysts, strengthens the basic side nature as NiO is impregnated [15,20]. Based on the findings, the qualitative analysis of CO 2 desorption shown in Table 1 revealed that 10% NiO/AS (207.6 mol g − 1 ) had the maximum CO 2 adsorption capacity of medium basic sites, followed by 5% NiO (26.9 mol g − 1 ) and 15% NiO/AS (18.4 mol g − 1 ). Strong basic sites expand as well in the following sequences: 15%NiO/AS (190.3 mol g − 1 ), 10%NiO/AS (424.8 mol g − 1 ), and 5%NiO/AS (133.6 mol g − 1 ) accordingly. It was discovered that strong basic sites had a significant impact on DRM reaction because the temperature of the reaction was remarkably closest to as temperature at CO 2 desorbed. Yet 10% NiO/AS had a greater possibility for DRM reaction because of its advanced strong basic sites rather than 5% and 15% NiO/AS, excessive strong CO 2 bonding with AS support resulted in large thermodynamics that necessary more energy to break these intermolecular bond [9]. Based on the qualities stated, 15%NiO/AS might be potential candidates for DRM reaction. Catalytic Performance of NiO/AS Catalysts Catalytic evaluations must be performed to determine reactant conversion, selectivity of desired product, and/or yield of product generated from the catalytic process in order to evaluate the superiority of produced catalysts. The stability and reusability of the catalyst toward deactivation are therefore equally important when investigating those attributes (Thybaut and Martin 2010 ). Figure 5 depicts the catalytic performance as it relates to NiO concentration, reaction temperature, catalyst loading, and gas hourly space velocity (GHSV). Initially, the impact of NiO concentration is investigated in order to determine the optimal xNiO/AS catalysts for the DRM process. As a result, only the best xNiO/AS catalysts were evaluated for the succeeding reaction temperature, catalyst loading, and GHSV. As previously described in the section on the physicochemical characteristics of xNiO/AS catalysts, NiO concentration is a critical parameter to consider in this work. As a result, the catalytic activity of 5–15% NiO concentration was found at optimal conditions previously described(Shamsuddin et al. 2021) CH 4 :CO 2 (50:50), 750°C, 2g catalyst, and GHSV 9000 h − 1 for 10 h reaction. Following that, Fig. 5 a depicted the conversion of CH 4 and CO 2 as well as the selectivity of H 2 and CO towards NiO concentration. Clearly, the 15%NiO/AS catalyst outperforms the others in terms of reactant conversion (90% CH 4 ; 80% CO 2 ) and product selectivity (50% H 2 ; 40% CO), with 5%NiO/AS (40% CH 4 & CO 2 ; 25% H 2 & CO) and 10%NiO/AS (30% CH 4 & 40%CO 2 ; 25%H 2 & 30% CO). The higher reactant conversions and selectivity of the product by 15%NiO/AS are attributed to the catalyst's physicochemical characteristics, which play a crucial part in boosting catalytic performance during the DRM process. It should be noted that the chemical properties of DRM govern its catalytic effectiveness. The rapid reducibility and strong basic sites of 15%NiO/AS correlated to better reactant conversion and product selectivity. Despite S BET and porosity being low compared to 10% NiO/AS, the percentage of NiO dispersion has a greater influence on DRM response. Therefore, it is possible that the reaction happened on the surface of the catalyst rather than in the constructed pore, where the greater distribution of NiO active sides boosted catalytic efficiency. Reactant conversion and product selectivity were shown in Fig. 5 B as a function of reaction temperature. Typically, the results show that around 90% of CH 4 and 80% of CO 2 had been converted, resulting in approximately 40–60% H 2 and CO selectivity. Yet, the reaction temperature of 800°C produced an unusual result due to a large drop in reactant conversion (approximately 85% CH 4 and 70% CO 2 ) and product selectivity (about 50% H 2 and 40% CO). It is expected that increasing the temperature of the reaction from 700°C to 900°C considerably improved catalytic performance. Nevertheless, the catalytic activity of 15%NiO/AS at 800°C was significantly reduced due to parallel reactions such as the water-gas shift (WGS) reaction Eq. (1–3) and CO disproportionation (Bourdouard reaction) Eq. (4) given in the following equation; water-gas shift (WGS) CO + H 2 O ⇌ CO 2 + H 2 , ∆H 298K = − 41 kJ mol − 1 (1) C + 2H 2 O ⇌ CO 2 + H 2 , ∆H 298K = + 90 kJ mol − 1 (2) H 2 O + C ⇌ CO + H 2 , ∆H 298K = + 131.3 kJ mol − 1 (3) CO disproportionation 2CO ⇌ C + CO 2 , ∆H 298K = − 172.4 kJ mol − 1 (4) Notably, WGS reactions that produced improved CO 2 utilizing CO as the reactant had worse catalytic performance primarily on CO 2 conversion and CO selectivity (refer to Eq. (1)). Hassan Amin and Bhargava confirmed that the WGS and Boudouard reactions occurred at temperatures lower than 817°C (1090K) and 701°C (974K), respectively. Since the ratio of H 2 /CO is almost unity over 817°C, WGS above that point may be ignorant (Hassan Amin 2018 ). In addition, this reversed trend was induced by outstanding decarbonization of CaCO 3 by CaCO 3 /CaO system on SiO 2 ideally at 800°C, as confirmed by Khosa and Zhao ( 2019 ). Figure 5 C was produced by conducting 15%NiO/AS evaluations with varied catalyst loadings packed on a reactor system. In accordance with the catalytic performance, increasing the catalyst loading reduces reactant conversions and selectivity of the products in the following order: 0.1 g > 0.2 g > 0.3g > 0.4g > 0.5g. The most favorable catalytic performance was achieved with 0.1 g catalyst loading, with > 95% CH 4 and CO 2 conversion and > 50% H 2 and CO selectivity. By adding 0.2 g 15NiO/AS catalyst with up to 60% H 2 selectivity, excellent H 2 production was achieved. Since catalyst loading correlated with the surface reaction of the reactant to the catalyst, too little loading may result in a lack of active sites on the catalyst. On the other hand, excessive loading might inhibit surface interaction between the reactant and active sides because the 'packed' state between particles limits the exposed surface on the catalyst. With respect to the results, it can be concluded that moderate catalyst loading increases catalytic performance in the DRM process, as agreed by Sulaiman et al. ( 2018 ) and Inga and Morsi ( 1997 ). The effect of GHSV on the catalytic performance of 15%NiO/AS is shown in Fig. 5 D, with reactant conversion ranging from 80–98% (CH 4 and CO 2 ); 60–65% for H 2 and 38–42% for CO selectivity, respectively. Despite GHSV 6000h − 1 demonstrating a modest decrease in reactant conversion, with around 82% CH 4 and 75% CO 2 conversion, this minor decline had no effect on total catalytic performance. Conceptually, GHSV is associated with the contact period between the reactant and catalyst, which was determined by the changing flow rates of all reactant mixtures (Yaghobi 2013 ). The extended contact durations resulted in increased product production by approaching thermodynamic equilibrium. Elkhalifa and Friedrich ( 2019 ) clarify that a longer duration of contact times which means low GHSV results in the higher formation of the product by reaching thermodynamic equilibrium. On the contrary, shorter contact times (greater GHSV) resulted in a sufficient period for the reactant and catalyst to react, followed by a decrease in catalytic performance. As a result, elevated GHSV likely lowered product selectivity by favouring homogeneous reactions. As a result of the outstanding physicochemical properties of the catalyst, 15%NiO/AS generated remarkable performance on GHSV from 3000 to 15000 h − 1 based on the GHSV plot. X-ray Photoelectron Spectroscopy (XPS) of fresh and spent catalysts XPS comparison studies for fresh and spent 15%NiO/AS to evaluate chemical states and surface species (element oxidation states) involved during DRM and created after the reaction. Figure 6 A depicted a wide deconvoluted peak for components found on pristine and spent catalysts. The elements discovered by the wide range scan from 0 to 1200 eV are Ni, O, C, Ca, and Si, which coincide with XRF analysis. All elements showed significant variations in peak intensity; Ni, O, Ca, and Si display low-intensity peaks due to low concentration after the DRM reaction except C. As a result, other elements were impeded by the high concentration of carbon, as shown by the high intensity of C peaks. Figure 6 B indicates a narrow scan of C1s that was implemented for peak correction as the reference value at a binding energy of 284.5 eV (Moulder and Chastain 1992 ). The observed spectra were fitted with three carbon species, including C1s (from carbon tape during sample preparation), C = O (287 eV), and CO 2 (290 eV) predicted from adsorbed-CO 2 on the catalyst surface. In contrast, the spent catalyst spectrum has identical peaks as the fresh catalyst spectrum together with two distinct peaks reflecting coke production from isolated carbon (C) at binding energy 285.1 eV and carbide species, Ni3C (283.8 eV). (Favaro et al. 2017 ) agreed that at 25°C (298K), CO 2 binds physically (physisorption) with a thin suboxide structure (in this instance CaO), as demonstrated by APXPS analysis. (Favaro et al. 2017 ). Thus, the isolated carbon and carbide species formation from XPS analysis was proven by (Zhang and Koka 1998 ). Figure 6 C shows a narrow scan from the core level element of Ni 2p with an energy binding range of 845 to 890 eV. The fresh catalyst exhibited significant peaks that corresponded to three Ni chemical states: NiO 3/2 (854.9 eV), Ni(OH) 2 3/2 (856.9 eV), and NiO satellite, correspondingly. The formation of nickel carbides (Ni 3 C) peaks at energy bound 852 eV caused substantial changes on 15%NiO/AS spent catalyst. Browning and Emmert (1952) recognized that the formation of Ni3C during the DRM reaction was associated with the CH 4 dissociation mechanism as the following equation (Browning and Emmett 1952 ). 3Ni + CH 4 ⇌ Ni 3 C + 2H 2 K 1 = (H 2 ) 2 /CH 4 (5) Thus, the free energy generated by Ni 3 C species demonstrates that it is a favourable reaction; nevertheless, the influence on the H 2 /CH 4 ratio is unaffected by this formation since free carbon formation is decreased or occurs gradually at low temperatures and is only affected by thermal diffusion and contaminants in the equilibrated gas (Browning and Emmett 1952 ). This Ni 3 C formation is consistence with C 1s peaks as discussed before. Evaluation of the support generates Figs. 6 D and 6 E, which were ascribed to the narrow scan of Si 2p and Ca 2p at binding energies of 98–110 eV and 342–354 eV, respectively. Based on the peaks observed, the pristine catalyst only shows SiO 2 peaks of 103.7 eV, which is consistent with those reported by (Senna et al. 2018 ). The formation of SiO 4 at BE = 106.2 eV, together with accessible SiO 2 peaks, considerably affects Si 2p binding energy. As a result, the drop in electron density near Si was followed by silicon oxidation from its normal state of Si 4+ to higher oxidation states. Additionally, the Ca 2p narrow scan reveals two noteworthy CaO and CaCO 3 peaks at binding energies of 346 eV and 347 eV, respectively. The formation of CaCO 3 is caused by adsorbed-CO 2 bonded into CaO, as seen by C1s peaks. Nevertheless, peak deconvolution of spent catalyst for Ca 2p is not feasible due to insufficient element concentration to discriminate between peaks and background scans. Meanwhile, as shown in Fig. 6 F, a narrow scan of O1s reveals the existence of three primary species. In accordance with the results, peaks of SiO (531.6 eV), CaO (530 eV), and NiO (529 eV) were identified. However, there are considerable changes adhering to the DRM reaction, particularly on SiO 2 peaks (533.6 eV), which were found on the spent catalyst. Hashimoto et al. concurred that this shifting can be attributed to the decrease of SiO 2 species caused by ion bombardment, which can result in changes in FWHM (full width at half-maximum) and chemical transformations (Hashimoto et al. 1992 ). Spent Catalysts Analysis In order to improve the catalyst's catalytic performance and stability/reusability, it is crucial to take into account coke production, sintering, and changes in chemical composition. Thus, Fig. 7 depicts the evaluation of the spent 15%NiO/AS catalyst using FESEM and TGA to monitor potential occurrences during and after a 10-hour DRM process. The empirical comparison of fresh (Fig. 7 A) and spent (Fig. 7 B) samples demonstrate evidence of carbon deposition and surface morphological changes that occur throughout the DRM reaction. Pristine catalyst surface morphology exhibits a 'towel-like' structure with nodules, as previously described. Yet adhering to the DRM reaction, the spent catalyst transforms into a fibrous structure with no nodules on the surface. The appearance of a nanotube structure in a higher magnification image is caused by the production of carbon nanotubes (CNTs) embedded in the catalyst surface with a diameter of around 60nm. It is widely acknowledged that the process of carbon or coke generation on the catalyst's surface during DRM involves two side reactions, namely CH 4 breakdown (Eq. (5)) and the Boudouard reaction (Eq. 6), as shown by the following equation (Arora and Prasad 2016 ); CH 4 ⇌ C + 2H 2 ∆H o = 75 kJ mol − 1 , ∆G = 2190-26.45T kJ mol − 1 (5) 2CO ⇌ C + CO 2 ∆H o = -171 kJ mol − 1 , ∆G = -39810 + 40.87T kJ mol − 1 (6) Based on the thermodynamic calculation, the equilibrium constant for this two sides reaction is given by K i = exp (- ∆G o i /RT). Thus, the coke formation were thermodynamically favoured if K 6 > α and K 7 > β which α = ( \({p}_{{H}_{2}}\) ^2 / \({p}_{{CH}_{4}}\) ^ )/ P 0 , β = ( \({p}_{{CO}_{2}}\) ^ / p CO ^2 )/ P 0 , P 0 = 105 Pa and p = partial pressures (Ginsburg et al. 2005 ). TGA and DTG thermograms were shown in Fig. 7 C, which are ascribed to material/chemical generated during the breakdown of 15%NiO/AS fresh and spent catalyst. The fresh catalyst exhibits three distinct degradation phases, beginning with the elimination of moisture content at T max =72°C (2.77% wt). Since SiO 2 and Ni(OH) 2 concentration increased water molecule adsorption, the 15%NiO/AS catalyst generated moister peaks in the TGA thermogram. Increases in temperature of up to 500°C resulted in a second degradation phase at T max =604°C caused by CaCO 3 breakdown on the catalyst's surface. As demonstrated by the XPS Ca 2p narrow scan, the appearance of CaCO 3 was removed as shown by Eq. (7); CaCO 3 (s) \(\underrightarrow{\varDelta }\) + CaO (s) + CO 2 (7) According to Eq. (7), the decomposition of CaCO 3 produced CaO and CO 2 . (Bilton et al. 2012 ) found that the breakdown of CaCO 3 began at 600 o C and is supported by traces of CaO at the same temperature (Bilton et al. 2012 ). In contrast, the spent catalyst begins to undergo degradation phases at T max =536°C, followed by T max =597°C. The formation of two distinct peaks might be attributed to the development of two different types of coke deposited on the catalyst's surface. There are several forms of carbon species deposited during the DRM process, including adsorbed/atomic carbon in surface carbide form (C); polymers/amorphous films (C); Ni carbide in bulk form (C); vermicular filaments or whiskers (C v ); and graphite (crystalline) platelets films (C c ) (Arora and Prasad 2016 ). It is anticipated that the decomposition of C v types of carbon species, which corresponded to CNT, was observed at T max =536 o C with 21.06%wt found based on TGA and DTG thermogram. C c forms of carbon are estimated to be degraded with 20.34%wt during TGA evaluation at T max =597 o C. Images obtained from FESEM (Fig. 7 B) demonstrate the production of filaments or whiskers and graphite kinds of carbon as a result of the filamentous uneven surface morphology identified on the spent catalyst. Increasing the temperature over T max =938 o C produced the final degradation caused by the SiO 2 breakdown or flaws in the support material. At the measured temperature, a substantial value of 3.16%wt was recorded on fresh catalysts but insignificant weight percentages on wasted catalysts due to extremely low weight loss. A previous study byHoffman et al. ( 1987 ) proved that at temperatures between 900°C and 1000°C, the oxide decomposition reaction of Si + SiO 2 → 2SiO caused a defect or decomposition in the SiO 2 structure during high-temperature annealing. Conclusions The remarkable catalytic performance of the DRM reaction carried out using a variety of NiO/AS catalysts demonstrates that industrial waste products may be used in the energy industry for sustainable growth. Physical characteristics like BET surface area and porosity of the catalyst do not have a significant impact, according to the physicochemical analysis of the prepared catalysts, but NiO percentages of dispersion and chemical characteristics like reducibility and basicity are crucial for catalysts to function effectively as catalysts. better NiO dispersion and basicity lead to better reactant conversion because active areas on the catalyst surface are more accessible. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. As a result of all of these good features, 15%NiO/AS exhibits excellent catalytic activity with the reactant. Declarations Acknowledgment This research was funded by a grant from Skim Penyelidikan Lantikan Baru, Universiti Malaysia Sabah (SLB 2252). Author contributions Conceptualization and writing—original draft: Mohd Razali Shamsuddin. Data collection, formal analysis, and investigation: Mohd Razali Shamsuddin. Writing—review and editing: Mohd Razali Shamsuddin, Teo Siow Hwa, Tengku Sharifah Marliza Tengku Azmi, Azizul Hakim Lahuri, Taufiq-Yap Yun Hin Resources and supervision: Taufiq-Yap Yun Hin. All authors read and approved the final manuscript. Funding This research was funded by a grant from Skim Penyelidikan Lantikan Baru, Universiti Malaysia Sabah (SLB 2252). Ethics approval Not applicable. Consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare no competing interests. References Anaya K, Olufemi Oni A, Kumar A (2023) Investigating the techno-economic and environmental performance of chemical looping technology for hydrogen production. Sustain Energy Technol Assess 56. https://doi.org/10.1016/j.seta.2022.103008 Aramouni NAK, Touma JG, Tarboush BA et al (2017) Catalyst design for dry reforming of methane: Analysis review. 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Int J Energy Res n/a. https://doi.org/https://doi.org/10.1002/er.6816 Shen YJ, Zhang YL, Gao F et al (2018) Influence of temperature on the microstructure deterioration of sandstone. Energies (Basel) 11:1–17. https://doi.org/10.3390/en11071753 Soled SL, Iglesia E, Fiato RA et al (2003) Control of metal dispersion and structure by changes in the solid-state chemistry of supported cobalt Fischer-Tropsch catalysts. Top Catal 26:101–109. https://doi.org/10.1023/B:TOCA.0000012990.83630.f9 Sulaiman SA, Roslan R, Inayat M, Yasin Naz M (2018) Effect of blending ratio and catalyst loading on co-gasification of wood chips and coconut waste. J Energy Inst 91:779–785. https://doi.org/10.1016/j.joei.2017.05.003 Sun H, Zhang Q, Wen J et al (2020) Applied Surface Science Insight into the role of CaO in coke-resistant over Ni-HMS catalysts for CO 2 reforming of methane. Appl Surf Sci 521:146395. https://doi.org/10.1016/j.apsusc.2020.146395 Thommes M, Kaneko K, Neimark AV et al (2015) Physisorption of gases, with special reference to the evaluation of surface area and pore size distribution (IUPAC Technical Report). Pure and Applied Chemistry 87:1051–1069. https://doi.org/10.1515/pac-2014-1117 Thybaut J, Martin G (2010) Testing of Catalytic Properties. Encyclopedia of Life Support Systems 2–5 Wysocka I, Hupka J, Rogala A (2019) Catalytic Activity of Nickel and Ruthenium–Nickel Catalysts Supported on SiO2, ZrO2, Al2O3, and MgAl2O4 in a Dry Reforming Process. Catalysts 1–13 Yaghobi N (2013) The role of gas hourly space velocity and feed composition for catalytic oxidative coupling of methane: Experimental study. J King Saud Univ - Eng Sci 25:1–10 Zhang L, Koka RV (1998) A study on the oxidation and carbon diffusion of TiC in alumina-titanium carbide ceramics using XPS and Raman spectroscopy. Mater Chem Phys 57:23–32. https://doi.org/10.1016/S0254-0584(98)00187-4 Cite Share Download PDF Status: Published Journal Publication published 18 Apr, 2024 Read the published version in Environmental Science and Pollution Research → Version 1 posted Editorial decision: Major Revision 06 Mar, 2024 Reviewers agreed at journal 27 Feb, 2024 Reviewers invited by journal 27 Feb, 2024 Editor invited by journal 26 Feb, 2024 Editor assigned by journal 09 Feb, 2024 First submitted to journal 01 Feb, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3869773","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":275352655,"identity":"c5a129e6-f197-4f8a-952e-3d17a595401e","order_by":0,"name":"MOHD RAZALI 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Putra Malaysia Fakulti Sains","correspondingAuthor":false,"prefix":"","firstName":"Yun","middleName":"Hin","lastName":"Taufiq-Yap","suffix":""}],"badges":[],"createdAt":"2024-01-16 12:29:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3869773/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3869773/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11356-024-33325-7","type":"published","date":"2024-04-18T22:34:12+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":51879447,"identity":"1c7ba5ce-b556-4821-9c93-47127742a75d","added_by":"auto","created_at":"2024-03-01 20:59:59","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":589817,"visible":true,"origin":"","legend":"\u003cp\u003eTextural properties A) N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherm B) BJH Pore Sized Distribution C) X-ray Diffraction pattern\u003c/p\u003e","description":"","filename":"Onlinefloatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/f2b8652517c64eb8dc4df97b.png"},{"id":51879450,"identity":"636bb73c-5cc3-4f76-9114-35921e95afa8","added_by":"auto","created_at":"2024-03-01 21:00:00","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":4068199,"visible":true,"origin":"","legend":"\u003cp\u003eSurface morphology by FESEM-EDX images A) AS B) 5%NiO/AS C) 10%NiO/AS D) 15%NiO/AS\u003c/p\u003e","description":"","filename":"Onlinefloatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/4b0924b59a95bc5e65584eed.png"},{"id":51879448,"identity":"107cc3a9-c01f-4132-be96-b957af30174a","added_by":"auto","created_at":"2024-03-01 20:59:59","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":354901,"visible":true,"origin":"","legend":"\u003cp\u003eReduction behavior A) TPR-H\u003csub\u003e2\u003c/sub\u003e and B) X-ray diffraction after reduced\u003c/p\u003e","description":"","filename":"Onlinefloatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/91978401de0194a4327575e0.png"},{"id":51879449,"identity":"e0b00d68-f0e7-4c36-9a09-1b219d0b4889","added_by":"auto","created_at":"2024-03-01 20:59:59","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":229587,"visible":true,"origin":"","legend":"\u003cp\u003eCO\u003csub\u003e2\u003c/sub\u003e desorption profiles of NiO/AS catalysts by TPD-CO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"Onlinefloatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/eb3386b18a0f976ddafa80ab.png"},{"id":51879451,"identity":"6fff5ec8-83d6-4c28-906c-e6f758b5efe7","added_by":"auto","created_at":"2024-03-01 21:00:00","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":342093,"visible":true,"origin":"","legend":"\u003cp\u003eCatalytic performance A) Effect of NiO concentration and 15%NiO/AS B) Effect of temperature of reaction C) Effect of catalysts loading D) Effect of GHSV\u003c/p\u003e","description":"","filename":"Onlinefloatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/4b6ee2b9b2d333ab7341e69f.png"},{"id":51879453,"identity":"9091e921-1304-4761-9638-2d4c42a3ecb9","added_by":"auto","created_at":"2024-03-01 21:00:00","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":928370,"visible":true,"origin":"","legend":"\u003cp\u003eComparison study of X-ray photoelectron spectroscopy (XPS) on pristine and spent of 15%NiO-AS catalyst; A) wide scan; and narrow scan of B) Ni2p C) C1s D) O1s\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/515288059125db6320db91c2.jpeg"},{"id":51879696,"identity":"f6c4f39e-f2db-422e-a953-c3da2cad018d","added_by":"auto","created_at":"2024-03-01 21:08:00","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":2738667,"visible":true,"origin":"","legend":"\u003cp\u003eSpent catalysts analysis A) FESEM fresh-15%NiO/AS B) FESEM spent-15%NiO/AS_800\u003csup\u003eo\u003c/sup\u003eC C) TGA and DTG of fresh and spent catalysts\u003c/p\u003e","description":"","filename":"Onlinefloatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/8336bdf9fe605819ac3a886b.png"},{"id":55690283,"identity":"fdc83573-10ed-4cb7-a353-6fc8550bc97e","added_by":"auto","created_at":"2024-05-01 22:34:27","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6335445,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3869773/v1/ee64380c-7822-484c-b3bd-7a313070c1b9.pdf"}],"financialInterests":"","formattedTitle":"Performance of NiO Doped on Alkaline Sludge from Waste Photovoltaic Industries for Catalytic Dry Reforming of Methane","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAlkaline sludge from wastewater treatment facilities in photovoltaic solar cell industries is a byproduct or waste material formed during the treatment of wastewater generated during the manufacturing operations of solar cells. Multiple stages of manufacturing in the photovoltaic (PV) solar cell industry, including cleaning, etching, chemical processing, and washing, can result in the development of wastewater containing different pollutants, chemicals, and particles. Alkaline sludge is the solid residue or slurry that emerges after treating wastewater with alkaline chemicals such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). In the wastewater treatment process, these alkaline materials are utilized to precipitate or coagulate heavy metals and other contaminants present in the wastewater as well as to neutralize acidic components.\u003c/p\u003e \u003cp\u003eSupports were critical in improving catalytic activity and reducing carbon deposition during methane dry reforming (Bradford and Vannice \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e1999\u003c/span\u003e). The fundamental supports used in dry reforming aided in the gasification of carbonaceous species, which reduced carbon deposition and prevented sintering (Lucr\u0026eacute;dio et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). Recent research on NiO-based catalysts used in DRM revealed a significant improvement in the catalytic system, particularly in reducing carbon growth by combining nickel particles together with basic metal oxide MgO and CaO (Sun et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) or incorporating SiO\u003csub\u003e2\u003c/sub\u003e (Wysocka et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Support with high oxygen mobility and a strong Lewis basicity (Aramouni et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) might be used to enhance resistance toward coke deposition.\u003c/p\u003e \u003cp\u003eDry reforming of methane (DRM) reaction is one of the best solutions in realizing this approach due to not only reduced CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e emissions to the environment, but it also produces more valuable H\u003csub\u003e2\u003c/sub\u003e as alternative energy which is cleaner and higher efficiency (Anaya et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Several constraints that would hinder the efficiency of DRM reaction in producing H\u003csub\u003e2\u003c/sub\u003e can be overcome by implementing excellent catalysts to the reaction. The NiO-based catalyst could be the better choice which is more economical compared to noble metal. Some improvements that hindered the reactivity and stability of NiO-based catalysts can be implemented such as introducing the basic element of Ca and/or Mg as support material. Therefore, this paper aims the utilization of low-coast material like AS will be contributed to the basic sites of the catalyst which enhanced catalytic activity and stability. The synergistic effect between effective NiO-based catalysts on DRM reaction together with the availability of basic sites in AS support materials will undergo higher catalytic performance on that reaction. Thus, application AS not only provides basic sites for the prepared catalyst but also shows the feasibility of these mineral and waste materials implemented in the catalytic reaction.\u003c/p\u003e"},{"header":"Materials and Method","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eMaterials\u003c/h2\u003e \u003cp\u003eThe chemicals used in the preparation of catalysts are Ni (NO\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.6H\u003csub\u003e2\u003c/sub\u003eO (ACROS with a purity of 99.8%) and AS. The AS resources for this study come from PV solar cell factory effluent in Bintulu, Malaysia. The elemental composition of AS was validated by XRF and was dominated by SiO\u003csub\u003e2\u003c/sub\u003e (61.93%), CaO (31.78%), Fe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (2.00%), Na\u003csub\u003e2\u003c/sub\u003eO(1.5%), Cl (1.18%), and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e (0.41%). Linde Malaysia Sdn. Bhd. supplied the reactant gas, which comprises high quality CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e at a concentration of CH\u003csub\u003e4\u003c/sub\u003e:CO\u003csub\u003e2\u003c/sub\u003e: = 50:50 vol.%.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eCatalyst preparation\u003c/h2\u003e \u003cp\u003ePrior to catalyst production, AS tended to be calcined at 900\u0026deg;C in an air environment. The impregnation technique was used to prepare NiO-supported AS with various Ni loadings and dispersed in distilled water. In order to achieve a homogeneous solution of prepared [x]NiO/talc (x\u0026thinsp;=\u0026thinsp;5, 10, 15 wt%), a complimentary quantity of AS and an adequate quantity of Ni salt were incorporated in 100 mL of distillate water and constantly stirred. The mixtures were then gently heated at 150\u0026deg;C to remove any remaining water before drying overnight at 100\u0026deg;C. The dried precursors were crushed into a fine powder and calcined at 600\u0026deg;C for 3 hours at a heating rate of 10\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the air atmosphere.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eCatalyst characterization\u003c/h2\u003e \u003cp\u003eThe N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption study was carried out at -196\u0026deg;C utilizing a Micromeritic ASAP2020 to quantify BET surface area, pore volume, and size. The sample was degassed at 150\u0026deg;C for 8 hours before identification to remove any water or other adsorbed gas from the catalyst surface. X-ray diffraction (XRD) (PANalytical X'Pert Pro-MPD diffractometer) coupled with a solid-state detector was used to determine the phase composition and the crystallite properties of catalysts. To identify the crystal phases of the produced catalyst, the results were recorded at 2θ between 5\u0026deg; and 80\u0026deg; with a scan speed of 4\u0026deg;min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. In preparation for pre-treatment, 0.05 g catalysts were placed into the quartz tube reactor (ID\u0026thinsp;=\u0026thinsp;6 mm) and treated for 10 minutes at 150\u0026deg;C under N\u003csub\u003e2\u003c/sub\u003e gas flow (20 mL min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). The procedure was conducted with a 5% H\u003csub\u003e2\u003c/sub\u003e/Ar flow rate of 25 mL min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e from room temperature to 950\u0026deg;C with a heating ramp of 10\u0026deg;C min\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. A field emission scanning electron microscope (FESEM; JEOL JSM-7600F) combined with an energy dispersive X-ray detector (Oxford INCA X-MAC 51 XMX 0021) was used to analyze the morphology and elemental content.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eCatalytic performance\u003c/h2\u003e \u003cp\u003eThe catalytic activities of the DRM reaction over NiO/AS were evaluated in a fixed bed stainless steel microreactor combined with a GC system (ID\u0026thinsp;=\u0026thinsp;6 mm) for 3 hours at varied temperatures (600 to 800\u0026deg;C) and reactant concentrations of CH\u003csub\u003e4\u003c/sub\u003e:CO\u003csub\u003e2\u003c/sub\u003e: = 50:50 vol.%. The gas product was identified using an Agilent 6890 N (G 1540 N) online gas chromatograph equipped with Varian capillary columns HP-PLOT/Q and HP-MOLSIV. The GC directly detected all gaseous concentrations in both the inlet and outlet streams. The equations were used to calculate CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e conversion (xCH\u003csub\u003e4\u003c/sub\u003e \u0026amp; xCO\u003csub\u003e2\u003c/sub\u003e) with H\u003csub\u003e2\u003c/sub\u003e and CO selectivity (SH\u003csub\u003e2\u003c/sub\u003e \u0026amp; SCO) as described by (Shamsuddin et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021c\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eTextural properties\u003c/h2\u003e \u003cp\u003eThe DRM catalytic performance is affected by the textural properties of the catalyst. As a result, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e depicts textural qualities in terms of surface area and porosity (N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption) as well as crystal phase (XRD). The N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherm of NiO/AS catalysts was depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA. All of the catalysts exhibit a type III isotherm with an H3 hysteresis loop. This shows that all NiO/AS catalysts are nonporous or macroporous solids with weak adsorbent-adsorbate interactions (Thommes et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Thus, the H3 form of the hysteresis loop reveals that these macroporous solids are made up of pore networks that are only partially filled with pore condensate (Thommes et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHowever, nickel impregnation boosted the produced catalysts' ability to adsorb, while also increasing BET surface area, S\u003csub\u003eBET\u003c/sub\u003e; pore size, and pore volume (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The following orders caused an increase in pore volume and SBET: 15% NiO/AS, 10% NiO/AS, and 5% NiO/AS It was discovered that increasing the NiO loading lowered S\u003csub\u003eBET\u003c/sub\u003e and pore volume due to pore obstruction by NiO particles (Shamsuddin et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e). Compared to 5%NiO/AS and 15%NiO/AS, 10%NiO/AS had the largest pore size because it formed larger pores (5\u0026ndash;50 nm). The pore size distribution of xNiO/AS catalysts is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB as bimodular porosity with small mesopore (4nm) and wide mesopore (5\u0026ndash;50 nm) (Groen et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Furthermore, when compared to others, 15%NiO/AS (refer to Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB*) has the largest distribution of narrow mesopore type. This demonstrates that metal addition displayed good sustentation of catalyst porosity (Kaydouh et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe phase composition of crystallized NiO/AS catalysts was shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC. All AS-supported catalysts produce SiO (JCPDS 01-0378) and 3CaO.2SiO\u003csub\u003e2\u003c/sub\u003e (JCPDS 02-0323). The intensity peaks of NiO (ICDD 00-022-1189) correspond to the planes of cubic NiO species and grow as NiO loading increases at 2θ (h,k,l)\u0026thinsp;=\u0026thinsp;37\u0026deg;(111), 43\u0026deg;(200), 62\u0026deg;(220), 75\u0026deg;(311), and 79\u0026deg;(222). Thus, the creation of intermetallic CaNi\u003csub\u003e5\u003c/sub\u003e (JCPDS 19\u0026ndash;0244) demonstrates a significant interaction between active metal (Nickel) and support (Penner and Armbr\u0026uuml;ster \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Additionally, NiO crystallite sizes (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) obtained using the Debye-Scherrer equation at 2θ\u0026thinsp;=\u0026thinsp;43\u0026deg; show that NiO/AS catalysts grew in the following orders: 5% NiO/AS, 15% NiO/AS, and 10% NiO/AS. As a result, Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e reveals that 15%NiO/AS has the most extensive NiO dispersion percentages when compared to 5%NiO/AS and 10%NiO/AS. In contrast to 15%NiO/AS, 10%NiO/AS showed a somewhat greater intensity of intermetallic CaNi\u003csub\u003e5\u003c/sub\u003e, which resulted in a lesser dispersion of NiO. In essence, the development of narrow mesopore types leads to an improvement in the size of the NiO crystallized phase and an increase in catalyst NiO dispersion.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003ePhysicochemical properties of NiO/AS catalysts\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperties\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eS\u003csub\u003eBET\u003c/sub\u003e\u003c/p\u003e \u003cp\u003e(m\u003csup\u003e2\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePore Size\u003c/p\u003e \u003cp\u003e(nm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePore Volume\u003c/p\u003e \u003cp\u003e(cm\u003csup\u003e3\u003c/sup\u003eg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNiO\u003c/p\u003e \u003cp\u003eCrystallite size (nm)*\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eNiO\u003c/p\u003e \u003cp\u003eDispersions (%)**\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c8\" namest=\"c7\"\u003e \u003cp\u003eTPR-H\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c10\" namest=\"c9\"\u003e \u003cp\u003eTPD-CO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCatalysts\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eTemp (℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eAmount\u003c/p\u003e \u003cp\u003e(\u0026micro;molg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eTemp\u003c/p\u003e \u003cp\u003e(℃)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eAmount\u003c/p\u003e \u003cp\u003e(\u0026micro;molg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4.99\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.33\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0065\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003en/a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003en/a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003en/a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003en/a\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e571\u003c/p\u003e \u003cp\u003e851\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e109.72\u003c/p\u003e \u003cp\u003e6.32\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e5%NiO/AS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e15.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e15.31\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0349\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e39.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e22.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e403\u003c/p\u003e \u003cp\u003e601\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e198.32\u003c/p\u003e \u003cp\u003e1709.74\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e307\u003c/p\u003e \u003cp\u003e693\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e26.88\u003c/p\u003e \u003cp\u003e133.56\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e10%NiO/AS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e13.21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e25.30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0345\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e66.98\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e37.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e439\u003c/p\u003e \u003cp\u003e603\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e267.14\u003c/p\u003e \u003cp\u003e2562.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e402\u003c/p\u003e \u003cp\u003e693\u003c/p\u003e \u003cp\u003e824\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e207.59\u003c/p\u003e \u003cp\u003e317.29\u003c/p\u003e \u003cp\u003e107.48\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e15%NiO/AS\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12.60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e17.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.0282\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e47.73\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e42.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e425\u003c/p\u003e \u003cp\u003e519\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1547.82\u003c/p\u003e \u003cp\u003e2045.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c9\"\u003e \u003cp\u003e399\u003c/p\u003e \u003cp\u003e723\u003c/p\u003e \u003cp\u003e784\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e18.41\u003c/p\u003e \u003cp\u003e154.61\u003c/p\u003e \u003cp\u003e35.74\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"10\"\u003e* derived from Debye-Scherrer equation obtained by NiO peaks at 2θ\u0026thinsp;=\u0026thinsp;43\u0026deg;\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e** derived from H\u003csub\u003e2\u003c/sub\u003e-TPR results as suggested by Fadoni et al. (1999).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eSurface morphology by FESEM-EDX\u003c/h2\u003e \u003cp\u003eThe xNiO/AS catalyst's surface morphological characteristics have been examined to ascertain the impact of the surface structure on the physicochemical properties of the developed catalyst. In accordance with Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, the images retrieved from the AS support (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA) showed a coral-like formation with several brunches all around the catalyst. It's interesting to note that the produced image displays hierarchical units attached together to form a coral shape made up of a number of aggregates resembling dendrites. As the quantity of NiO loading on support increases, it is added gradually to AS modifications.\u003c/p\u003e \u003cp\u003eImages of a 5%NiO/AS catalyst in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB demonstrate very minor alterations to the catalyst's structural integrity. Images at higher magnification show the development of nodules at a specific location on the surface of the catalysts. These nodules' presence is evidence that AS's surface was effectively impregnated with NiO. This impregnation is therefore demonstrated by an elevated plot level (approximately 5%) of EDX. The surface morphology of the catalyst is significantly altered when the NiO loading is increased by 10% (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eC). A towel-like structure has formed on the catalyst's surface subsequent to the coral-like structure collapsing. Apart from that, larger NiO particles started to emerge between the AS structure's gaps. Numerous nodule particles (grainy-like) were scattered on these towel-like structures as a result of higher impregnation of NiO up to 15%. A high-magnification image demonstrates evenly distributed rough particles, supporting the conclusion of the NiO dispersion degree (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). As a result, these exceptional qualities are anticipated to enhance DRM catalytic performance.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eReduction behavior\u003c/h2\u003e \u003cp\u003eTo explore reduction behaviors, the estimated oxygen storage capacity of each metal oxide was measured using the TPR-H\u003csub\u003e2\u003c/sub\u003e analysis (Samsuri et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The reducibility. The reducibility of active metals is crucial in the DRM reaction because it offers vacancy active sides, which oxygen abandons throughout the reduction process (Puigdollers et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). According to TPR-H\u003csub\u003e2\u003c/sub\u003e analysis conditions, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea depicts the reduction behavior of NiO/AS catalysts. The flat line on the TPR-H\u003csub\u003e2\u003c/sub\u003e spectra indicates that, as would be anticipated, oxides like SiO\u003csub\u003e2\u003c/sub\u003e and CaO in AS support were not reducible (Puigdollers et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Significantly distinct peaks are produced when nickel is impregnated into an AS support, and these peaks correlate to the reduction behavior of NiO species on catalysts. Most NiO/AS catalysts displayed two dominating peaks, each of which indicated two reduction processes. The first notable peak occurs between 300\u003csup\u003eo\u003c/sup\u003eC and 450\u003csup\u003eo\u003c/sup\u003eC owing to the reduction of Ni\u003csup\u003e2+\u003c/sup\u003e to Ni\u003csup\u003e0\u003c/sup\u003e species on the surface of catalysts (Shamsuddin et al. \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021b\u003c/span\u003e). Evidently, 15%NiO/AS exhibits the maximum quantity and intensity (see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea) at lower temperatures when compared to 5%NiO/AS and 10%NiO/AS. Metal-support interaction has been found to be substantially linked with catalyst reducibility. At lower temperatures, a decreased peak was created by weak contact between NiO and the AS support. However, significant interaction results in a greater temperature peak decrease. The above finding is consistent with(Lokteva and Golubina (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) that lower metal loading would result in less metal-support interaction.\u003c/p\u003e \u003cp\u003eAdditionally, the larger dispersion of NiO species in catalyst surfaces also had an impact on the low reduction temperature. As NiO loadings were increased, the percentages of dispersion of NiO in produced NiO/AS catalysts increased. Furthermore, the lowest peak intensity of 10%NiO/AS indicates that the NiO species in this catalyst is in a bulky form (largest NiO crystallite size), which is harder to reduce and may interfere with the catalyst's catalytic behaviours. As a result, the size of the crystallites increases in the following order: 5% NiO/AS, 15% NiO/AS, and 10% NiO/AS. According to (Soled et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e), the strong association of metal to support makes it more difficult to decrease than related bulk metal oxides(Soled et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Consequently, greater reduction temperatures must be achieved to provide an active metal phase, resulting in poor metal dispersion. In contrast, poor metal-support interactions result in outstanding metal oxide dispersion and decreased crystallite size, resulting in reductions at lower temperatures (Soled et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2003\u003c/span\u003e). Therefore, an appropriate compromise between the support and the precursor could be reached by optimal metal loading, which improved metal oxide dispersion, crystallite size, and reducibility behaviors.\u003c/p\u003e \u003cp\u003eThe subsequent findings (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB) were obtained by XRD scanning of reduced-xNiO/AS catalysts under the same conditions. The comparative investigation of NiO/AS with reduced-xNiO/AS catalysts reveals the production of new metallic Ni (ICDD 01-087-0712) phases at 2θ\u0026thinsp;=\u0026thinsp;44.5\u0026deg; (111), 51.8 (200), and 76.4 (220), which greatly obliterate the NiO phase in the diffractogram. SiO\u003csub\u003e2\u003c/sub\u003e (ICDD 01-0378), 3CaO.2SiO\u003csub\u003e2\u003c/sub\u003e (ICDD 02-0323), and CaNi5 (ICDD 19\u0026ndash;0244) phases all show significant modifications. The peak intensities of 3CaO.2SiO\u003csub\u003e2\u003c/sub\u003e and CaNi\u003csub\u003e5\u003c/sub\u003e were slightly less intense than those of the SiO\u003csub\u003e2\u003c/sub\u003e peaks due to the high-temperature impact observed during TPR-H\u003csub\u003e2\u003c/sub\u003e analysis compared to the NiO/AS catalyst. It has been established that ranging materials' response to temperature affected the change of lattice parameters and the decomposed (Shen et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eBasic sites properties\u003c/h2\u003e \u003cp\u003eThe core of the catalytic DRM process is initiated by acid-base interactions and is sustained by reaction cycles. Particularly, CO\u003csub\u003e2\u003c/sub\u003e reagents are strong acidic molecules and only interact with the catalyst with basic sites. Precisely as a result, basic sites play an essential part in enhancing acidic CO\u003csub\u003e2\u003c/sub\u003e activation, inhibiting carbon formation on active sites, and enhancing catalytic durability [19]. TPD-CO\u003csub\u003e2\u003c/sub\u003e may therefore be used to evaluate these basic sites and their unique characteristics in both quantities and qualitatively. Corresponding to the CO\u003csub\u003e2\u003c/sub\u003e desorption temperature, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e showed three types of basic strength, which were weak (250\u0026deg;C), medium (250\u0026ndash;500\u0026deg;C), and strong (\u0026gt;\u0026thinsp;500\u0026deg;C) (Lahuri et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). The strongest basic sites are typically found at temperatures of 571\u0026deg;C and 851\u0026deg;C, by AS support. The formation of CO\u003csub\u003e2\u003c/sub\u003e ligands such as monodentate, bidentate, polydentate, and bicarbonate species between the CO\u003csub\u003e2\u003c/sub\u003e reactant and CaO basic sites matched these strong basic sites [9]. The availability of CaO as a basic site is less abundant than SiO\u003csub\u003e2\u003c/sub\u003e, which results in a somewhat decreased CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity in this support (see Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Consequently, XRD analysis demonstrated that the production of intermediate species of 3CaO.2SiO\u003csub\u003e2\u003c/sub\u003e reduced the creation of CO\u003csub\u003e2\u003c/sub\u003e ligands.\u003c/p\u003e \u003cp\u003eIn comparison to AS support, the TPD-CO\u003csub\u003e2\u003c/sub\u003e profiles of xNiO/AS catalysts exhibit substantial variations due to the resulting formation of moderate basic sites and peak shifting of strong basic sites. The presence of free O\u003csup\u003e2\u0026minus;\u003c/sup\u003e anions from the NiO species, which are provided by surface defects on the catalysts, strengthens the basic side nature as NiO is impregnated [15,20]. Based on the findings, the qualitative analysis of CO\u003csub\u003e2\u003c/sub\u003e desorption shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e revealed that 10% NiO/AS (207.6 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) had the maximum CO\u003csub\u003e2\u003c/sub\u003e adsorption capacity of medium basic sites, followed by 5% NiO (26.9 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) and 15% NiO/AS (18.4 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Strong basic sites expand as well in the following sequences: 15%NiO/AS (190.3 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), 10%NiO/AS (424.8 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), and 5%NiO/AS (133.6 mol g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) accordingly. It was discovered that strong basic sites had a significant impact on DRM reaction because the temperature of the reaction was remarkably closest to as temperature at CO\u003csub\u003e2\u003c/sub\u003e desorbed. Yet 10% NiO/AS had a greater possibility for DRM reaction because of its advanced strong basic sites rather than 5% and 15% NiO/AS, excessive strong CO\u003csub\u003e2\u003c/sub\u003e bonding with AS support resulted in large thermodynamics that necessary more energy to break these intermolecular bond [9]. Based on the qualities stated, 15%NiO/AS might be potential candidates for DRM reaction.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003eCatalytic Performance of NiO/AS Catalysts\u003c/h2\u003e \u003cp\u003eCatalytic evaluations must be performed to determine reactant conversion, selectivity of desired product, and/or yield of product generated from the catalytic process in order to evaluate the superiority of produced catalysts. The stability and reusability of the catalyst toward deactivation are therefore equally important when investigating those attributes (Thybaut and Martin \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e depicts the catalytic performance as it relates to NiO concentration, reaction temperature, catalyst loading, and gas hourly space velocity (GHSV). Initially, the impact of NiO concentration is investigated in order to determine the optimal xNiO/AS catalysts for the DRM process. As a result, only the best xNiO/AS catalysts were evaluated for the succeeding reaction temperature, catalyst loading, and GHSV.\u003c/p\u003e \u003cp\u003eAs previously described in the section on the physicochemical characteristics of xNiO/AS catalysts, NiO concentration is a critical parameter to consider in this work. As a result, the catalytic activity of 5\u0026ndash;15% NiO concentration was found at optimal conditions previously described(Shamsuddin et al. 2021) CH\u003csub\u003e4\u003c/sub\u003e:CO\u003csub\u003e2\u003c/sub\u003e (50:50), 750\u0026deg;C, 2g catalyst, and GHSV 9000 h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e for 10 h reaction. Following that, Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea depicted the conversion of CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e as well as the selectivity of H\u003csub\u003e2\u003c/sub\u003e and CO towards NiO concentration. Clearly, the 15%NiO/AS catalyst outperforms the others in terms of reactant conversion (90% CH\u003csub\u003e4\u003c/sub\u003e; 80% CO\u003csub\u003e2\u003c/sub\u003e) and product selectivity (50% H\u003csub\u003e2\u003c/sub\u003e; 40% CO), with 5%NiO/AS (40% CH\u003csub\u003e4\u003c/sub\u003e \u0026amp; CO\u003csub\u003e2\u003c/sub\u003e; 25% H\u003csub\u003e2\u003c/sub\u003e \u0026amp; CO) and 10%NiO/AS (30% CH\u003csub\u003e4\u003c/sub\u003e \u0026amp; 40%CO\u003csub\u003e2\u003c/sub\u003e; 25%H\u003csub\u003e2\u003c/sub\u003e \u0026amp; 30% CO). The higher reactant conversions and selectivity of the product by 15%NiO/AS are attributed to the catalyst's physicochemical characteristics, which play a crucial part in boosting catalytic performance during the DRM process. It should be noted that the chemical properties of DRM govern its catalytic effectiveness. The rapid reducibility and strong basic sites of 15%NiO/AS correlated to better reactant conversion and product selectivity. Despite S\u003csub\u003eBET\u003c/sub\u003e and porosity being low compared to 10% NiO/AS, the percentage of NiO dispersion has a greater influence on DRM response. Therefore, it is possible that the reaction happened on the surface of the catalyst rather than in the constructed pore, where the greater distribution of NiO active sides boosted catalytic efficiency.\u003c/p\u003e \u003cp\u003eReactant conversion and product selectivity were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB as a function of reaction temperature. Typically, the results show that around 90% of CH\u003csub\u003e4\u003c/sub\u003e and 80% of CO\u003csub\u003e2\u003c/sub\u003e had been converted, resulting in approximately 40\u0026ndash;60% H\u003csub\u003e2\u003c/sub\u003e and CO selectivity. Yet, the reaction temperature of 800\u0026deg;C produced an unusual result due to a large drop in reactant conversion (approximately 85% CH\u003csub\u003e4\u003c/sub\u003e and 70% CO\u003csub\u003e2\u003c/sub\u003e) and product selectivity (about 50% H\u003csub\u003e2\u003c/sub\u003e and 40% CO). It is expected that increasing the temperature of the reaction from 700\u0026deg;C to 900\u0026deg;C considerably improved catalytic performance. Nevertheless, the catalytic activity of 15%NiO/AS at 800\u0026deg;C was significantly reduced due to parallel reactions such as the water-gas shift (WGS) reaction Eq.\u0026nbsp;(1\u0026ndash;3) and CO disproportionation (Bourdouard reaction) Eq.\u0026nbsp;(4) given in the following equation;\u003c/p\u003e \u003cp\u003e \u003cb\u003ewater-gas shift (WGS)\u003c/b\u003e CO\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003eO ⇌ CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003e, ∆H \u003csub\u003e298K\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;41 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (1)\u003c/p\u003e \u003cp\u003eC\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003eO ⇌ CO\u003csub\u003e2\u003c/sub\u003e\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003e, ∆H \u003csub\u003e298K\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;+\u0026thinsp;90 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (2)\u003c/p\u003e \u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO\u0026thinsp;+\u0026thinsp;C ⇌ CO\u0026thinsp;+\u0026thinsp;H\u003csub\u003e2\u003c/sub\u003e, ∆H \u003csub\u003e298K\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;+\u0026thinsp;131.3 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (3)\u003c/p\u003e \u003cp\u003e \u003cb\u003eCO disproportionation\u003c/b\u003e 2CO ⇌ C\u0026thinsp;+\u0026thinsp;CO\u003csub\u003e2\u003c/sub\u003e, ∆H \u003csub\u003e298K\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;172.4 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (4)\u003c/p\u003e \u003cp\u003eNotably, WGS reactions that produced improved CO\u003csub\u003e2\u003c/sub\u003e utilizing CO as the reactant had worse catalytic performance primarily on CO\u003csub\u003e2\u003c/sub\u003e conversion and CO selectivity (refer to Eq.\u0026nbsp;(1)). Hassan Amin and Bhargava confirmed that the WGS and Boudouard reactions occurred at temperatures lower than 817\u0026deg;C (1090K) and 701\u0026deg;C (974K), respectively. Since the ratio of H\u003csub\u003e2\u003c/sub\u003e/CO is almost unity over 817\u0026deg;C, WGS above that point may be ignorant (Hassan Amin \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). In addition, this reversed trend was induced by outstanding decarbonization of CaCO\u003csub\u003e3\u003c/sub\u003e by CaCO\u003csub\u003e3\u003c/sub\u003e/CaO system on SiO\u003csub\u003e2\u003c/sub\u003e ideally at 800\u0026deg;C, as confirmed by Khosa and Zhao (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eC was produced by conducting 15%NiO/AS evaluations with varied catalyst loadings packed on a reactor system. In accordance with the catalytic performance, increasing the catalyst loading reduces reactant conversions and selectivity of the products in the following order: 0.1 g\u0026thinsp;\u0026gt;\u0026thinsp;0.2 g\u0026thinsp;\u0026gt;\u0026thinsp;0.3g\u0026thinsp;\u0026gt;\u0026thinsp;0.4g\u0026thinsp;\u0026gt;\u0026thinsp;0.5g. The most favorable catalytic performance was achieved with 0.1 g catalyst loading, with \u0026gt;\u0026thinsp;95% CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e conversion and \u0026gt;\u0026thinsp;50% H\u003csub\u003e2\u003c/sub\u003e and CO selectivity. By adding 0.2 g 15NiO/AS catalyst with up to 60% H\u003csub\u003e2\u003c/sub\u003e selectivity, excellent H\u003csub\u003e2\u003c/sub\u003e production was achieved. Since catalyst loading correlated with the surface reaction of the reactant to the catalyst, too little loading may result in a lack of active sites on the catalyst. On the other hand, excessive loading might inhibit surface interaction between the reactant and active sides because the 'packed' state between particles limits the exposed surface on the catalyst. With respect to the results, it can be concluded that moderate catalyst loading increases catalytic performance in the DRM process, as agreed by Sulaiman et al. (\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2018\u003c/span\u003e) and Inga and Morsi (\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1997\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe effect of GHSV on the catalytic performance of 15%NiO/AS is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD, with reactant conversion ranging from 80\u0026ndash;98% (CH\u003csub\u003e4\u003c/sub\u003e and CO\u003csub\u003e2\u003c/sub\u003e); 60\u0026ndash;65% for H\u003csub\u003e2\u003c/sub\u003e and 38\u0026ndash;42% for CO selectivity, respectively. Despite GHSV 6000h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e demonstrating a modest decrease in reactant conversion, with around 82% CH\u003csub\u003e4\u003c/sub\u003e and 75% CO\u003csub\u003e2\u003c/sub\u003e conversion, this minor decline had no effect on total catalytic performance. Conceptually, GHSV is associated with the contact period between the reactant and catalyst, which was determined by the changing flow rates of all reactant mixtures (Yaghobi \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The extended contact durations resulted in increased product production by approaching thermodynamic equilibrium. Elkhalifa and Friedrich (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) clarify that a longer duration of contact times which means low GHSV results in the higher formation of the product by reaching thermodynamic equilibrium. On the contrary, shorter contact times (greater GHSV) resulted in a sufficient period for the reactant and catalyst to react, followed by a decrease in catalytic performance. As a result, elevated GHSV likely lowered product selectivity by favouring homogeneous reactions. As a result of the outstanding physicochemical properties of the catalyst, 15%NiO/AS generated remarkable performance on GHSV from 3000 to 15000 h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e based on the GHSV plot.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003eX-ray Photoelectron Spectroscopy (XPS) of fresh and spent catalysts\u003c/h2\u003e \u003cp\u003eXPS comparison studies for fresh and spent 15%NiO/AS to evaluate chemical states and surface species (element oxidation states) involved during DRM and created after the reaction. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA depicted a wide deconvoluted peak for components found on pristine and spent catalysts. The elements discovered by the wide range scan from 0 to 1200 eV are Ni, O, C, Ca, and Si, which coincide with XRF analysis. All elements showed significant variations in peak intensity; Ni, O, Ca, and Si display low-intensity peaks due to low concentration after the DRM reaction except C. As a result, other elements were impeded by the high concentration of carbon, as shown by the high intensity of C peaks.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eB indicates a narrow scan of C1s that was implemented for peak correction as the reference value at a binding energy of 284.5 eV (Moulder and Chastain \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1992\u003c/span\u003e). The observed spectra were fitted with three carbon species, including C1s (from carbon tape during sample preparation), C\u0026thinsp;=\u0026thinsp;O (287 eV), and CO\u003csub\u003e2\u003c/sub\u003e (290 eV) predicted from adsorbed-CO\u003csub\u003e2\u003c/sub\u003e on the catalyst surface. In contrast, the spent catalyst spectrum has identical peaks as the fresh catalyst spectrum together with two distinct peaks reflecting coke production from isolated carbon (C) at binding energy 285.1 eV and carbide species, Ni3C (283.8 eV). (Favaro et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) agreed that at 25\u0026deg;C (298K), CO\u003csub\u003e2\u003c/sub\u003e binds physically (physisorption) with a thin suboxide structure (in this instance CaO), as demonstrated by APXPS analysis. (Favaro et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Thus, the isolated carbon and carbide species formation from XPS analysis was proven by (Zhang and Koka \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e1998\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC shows a narrow scan from the core level element of Ni 2p with an energy binding range of 845 to 890 eV. The fresh catalyst exhibited significant peaks that corresponded to three Ni chemical states: NiO 3/2 (854.9 eV), Ni(OH)\u003csub\u003e2\u003c/sub\u003e 3/2 (856.9 eV), and NiO satellite, correspondingly. The formation of nickel carbides (Ni\u003csub\u003e3\u003c/sub\u003eC) peaks at energy bound 852 eV caused substantial changes on 15%NiO/AS spent catalyst. Browning and Emmert (1952) recognized that the formation of \u003csub\u003eNi3C\u003c/sub\u003e during the DRM reaction was associated with the CH\u003csub\u003e4\u003c/sub\u003e dissociation mechanism as the following equation (Browning and Emmett \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1952\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e3Ni\u0026thinsp;+\u0026thinsp;CH\u003csub\u003e4\u003c/sub\u003e ⇌ Ni\u003csub\u003e3\u003c/sub\u003eC\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003e K\u003csub\u003e1\u003c/sub\u003e = (H\u003csub\u003e2\u003c/sub\u003e)\u003csup\u003e2\u003c/sup\u003e/CH\u003csub\u003e4\u003c/sub\u003e (5)\u003c/p\u003e \u003cp\u003eThus, the free energy generated by Ni\u003csub\u003e3\u003c/sub\u003eC species demonstrates that it is a favourable reaction; nevertheless, the influence on the H\u003csub\u003e2\u003c/sub\u003e/CH\u003csub\u003e4\u003c/sub\u003e ratio is unaffected by this formation since free carbon formation is decreased or occurs gradually at low temperatures and is only affected by thermal diffusion and contaminants in the equilibrated gas (Browning and Emmett \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e1952\u003c/span\u003e). This Ni\u003csub\u003e3\u003c/sub\u003eC formation is consistence with C 1s peaks as discussed before.\u003c/p\u003e \u003cp\u003eEvaluation of the support generates Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eD and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eE, which were ascribed to the narrow scan of Si 2p and Ca 2p at binding energies of 98\u0026ndash;110 eV and 342\u0026ndash;354 eV, respectively. Based on the peaks observed, the pristine catalyst only shows SiO\u003csub\u003e2\u003c/sub\u003e peaks of 103.7 eV, which is consistent with those reported by (Senna et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The formation of SiO\u003csub\u003e4\u003c/sub\u003e at BE\u0026thinsp;=\u0026thinsp;106.2 eV, together with accessible SiO\u003csub\u003e2\u003c/sub\u003e peaks, considerably affects Si 2p binding energy. As a result, the drop in electron density near Si was followed by silicon oxidation from its normal state of Si\u003csup\u003e4+\u003c/sup\u003e to higher oxidation states. Additionally, the Ca 2p narrow scan reveals two noteworthy CaO and CaCO\u003csub\u003e3\u003c/sub\u003e peaks at binding energies of 346 eV and 347 eV, respectively. The formation of CaCO\u003csub\u003e3\u003c/sub\u003e is caused by adsorbed-CO\u003csub\u003e2\u003c/sub\u003e bonded into CaO, as seen by C1s peaks. Nevertheless, peak deconvolution of spent catalyst for Ca 2p is not feasible due to insufficient element concentration to discriminate between peaks and background scans. Meanwhile, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eF, a narrow scan of O1s reveals the existence of three primary species. In accordance with the results, peaks of SiO (531.6 eV), CaO (530 eV), and NiO (529 eV) were identified. However, there are considerable changes adhering to the DRM reaction, particularly on SiO\u003csub\u003e2\u003c/sub\u003e peaks (533.6 eV), which were found on the spent catalyst. Hashimoto et al. concurred that this shifting can be attributed to the decrease of SiO\u003csub\u003e2\u003c/sub\u003e species caused by ion bombardment, which can result in changes in FWHM (full width at half-maximum) and chemical transformations (Hashimoto et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e1992\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003eSpent Catalysts Analysis\u003c/h2\u003e \u003cp\u003eIn order to improve the catalyst's catalytic performance and stability/reusability, it is crucial to take into account coke production, sintering, and changes in chemical composition. Thus, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e depicts the evaluation of the spent 15%NiO/AS catalyst using FESEM and TGA to monitor potential occurrences during and after a 10-hour DRM process. The empirical comparison of fresh (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA) and spent (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB) samples demonstrate evidence of carbon deposition and surface morphological changes that occur throughout the DRM reaction. Pristine catalyst surface morphology exhibits a 'towel-like' structure with nodules, as previously described. Yet adhering to the DRM reaction, the spent catalyst transforms into a fibrous structure with no nodules on the surface. The appearance of a nanotube structure in a higher magnification image is caused by the production of carbon nanotubes (CNTs) embedded in the catalyst surface with a diameter of around 60nm. It is widely acknowledged that the process of carbon or coke generation on the catalyst's surface during DRM involves two side reactions, namely CH\u003csub\u003e4\u003c/sub\u003e breakdown (Eq.\u0026nbsp;(5)) and the Boudouard reaction (Eq.\u0026nbsp;6), as shown by the following equation (Arora and Prasad \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e);\u003c/p\u003e \u003cp\u003eCH\u003csub\u003e4\u003c/sub\u003e ⇌ C\u0026thinsp;+\u0026thinsp;2H\u003csub\u003e2\u003c/sub\u003e ∆H\u003csup\u003eo\u003c/sup\u003e = 75 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, ∆G\u0026thinsp;=\u0026thinsp;2190-26.45T kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (5)\u003c/p\u003e \u003cp\u003e2CO ⇌ C\u0026thinsp;+\u0026thinsp;CO\u003csub\u003e2\u003c/sub\u003e ∆H\u003csup\u003eo\u003c/sup\u003e = -171 kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, ∆G = -39810\u0026thinsp;+\u0026thinsp;40.87T kJ mol\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (6)\u003c/p\u003e \u003cp\u003eBased on the thermodynamic calculation, the equilibrium constant for this two sides reaction is given by K\u003csub\u003ei\u003c/sub\u003e = exp (- ∆G\u003csup\u003eo\u003c/sup\u003e\u003csub\u003ei\u003c/sub\u003e /RT). Thus, the coke formation were thermodynamically favoured if K\u003csub\u003e6\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;α and K\u003csub\u003e7\u003c/sub\u003e\u0026thinsp;\u0026gt;\u0026thinsp;β which α = (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({p}_{{H}_{2}}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e^2\u003c/sup\u003e / \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({p}_{{CH}_{4}}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e^\u003c/sup\u003e)/ P\u003csub\u003e0\u003c/sub\u003e, β = (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({p}_{{CO}_{2}}\\)\u003c/span\u003e\u003c/span\u003e\u003csup\u003e^\u003c/sup\u003e / p\u003csub\u003eCO\u003c/sub\u003e \u003csup\u003e^2\u003c/sup\u003e)/ P\u003csub\u003e0\u003c/sub\u003e, P\u003csub\u003e0\u003c/sub\u003e\u0026thinsp;=\u0026thinsp;105 Pa and p\u0026thinsp;=\u0026thinsp;partial pressures (Ginsburg et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eTGA and DTG thermograms were shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eC, which are ascribed to material/chemical generated during the breakdown of 15%NiO/AS fresh and spent catalyst. The fresh catalyst exhibits three distinct degradation phases, beginning with the elimination of moisture content at T\u003csub\u003emax\u003c/sub\u003e=72\u0026deg;C (2.77% wt). Since SiO\u003csub\u003e2\u003c/sub\u003e and Ni(OH)\u003csub\u003e2\u003c/sub\u003e concentration increased water molecule adsorption, the 15%NiO/AS catalyst generated moister peaks in the TGA thermogram. Increases in temperature of up to 500\u0026deg;C resulted in a second degradation phase at T\u003csub\u003emax\u003c/sub\u003e=604\u0026deg;C caused by CaCO\u003csub\u003e3\u003c/sub\u003e breakdown on the catalyst's surface. As demonstrated by the XPS Ca 2p narrow scan, the appearance of CaCO\u003csub\u003e3\u003c/sub\u003e was removed as shown by Eq.\u0026nbsp;(7);\u003c/p\u003e \u003cp\u003eCaCO\u003csub\u003e3\u003c/sub\u003e (s) \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\underrightarrow{\\varDelta }\\)\u003c/span\u003e\u003c/span\u003e + CaO (s)\u0026thinsp;+\u0026thinsp;CO\u003csub\u003e2\u003c/sub\u003e (7)\u003c/p\u003e \u003cp\u003eAccording to Eq.\u0026nbsp;(7), the decomposition of CaCO\u003csub\u003e3\u003c/sub\u003e produced CaO and CO\u003csub\u003e2\u003c/sub\u003e. (Bilton et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) found that the breakdown of CaCO\u003csub\u003e3\u003c/sub\u003e began at 600\u003csup\u003eo\u003c/sup\u003eC and is supported by traces of CaO at the same temperature (Bilton et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2012\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn contrast, the spent catalyst begins to undergo degradation phases at T\u003csub\u003emax\u003c/sub\u003e=536\u0026deg;C, followed by T\u003csub\u003emax\u003c/sub\u003e=597\u0026deg;C. The formation of two distinct peaks might be attributed to the development of two different types of coke deposited on the catalyst's surface. There are several forms of carbon species deposited during the DRM process, including adsorbed/atomic carbon in surface carbide form (C); polymers/amorphous films (C); Ni carbide in bulk form (C); vermicular filaments or whiskers (C\u003csub\u003ev\u003c/sub\u003e); and graphite (crystalline) platelets films (C\u003csub\u003ec\u003c/sub\u003e) (Arora and Prasad \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). It is anticipated that the decomposition of C\u003csub\u003ev\u003c/sub\u003e types of carbon species, which corresponded to CNT, was observed at T\u003csub\u003emax\u003c/sub\u003e=536\u003csup\u003eo\u003c/sup\u003eC with 21.06%wt found based on TGA and DTG thermogram. C\u003csub\u003ec\u003c/sub\u003e forms of carbon are estimated to be degraded with 20.34%wt during TGA evaluation at T\u003csub\u003emax\u003c/sub\u003e=597\u003csup\u003eo\u003c/sup\u003eC. Images obtained from FESEM (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB) demonstrate the production of filaments or whiskers and graphite kinds of carbon as a result of the filamentous uneven surface morphology identified on the spent catalyst. Increasing the temperature over T\u003csub\u003emax\u003c/sub\u003e=938\u003csup\u003eo\u003c/sup\u003eC produced the final degradation caused by the SiO\u003csub\u003e2\u003c/sub\u003e breakdown or flaws in the support material. At the measured temperature, a substantial value of 3.16%wt was recorded on fresh catalysts but insignificant weight percentages on wasted catalysts due to extremely low weight loss. A previous study byHoffman et al. (\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1987\u003c/span\u003e) proved that at temperatures between 900\u0026deg;C and 1000\u0026deg;C, the oxide decomposition reaction of Si\u0026thinsp;+\u0026thinsp;SiO\u003csub\u003e2\u003c/sub\u003e \u0026rarr; 2SiO caused a defect or decomposition in the SiO\u003csub\u003e2\u003c/sub\u003e structure during high-temperature annealing.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe remarkable catalytic performance of the DRM reaction carried out using a variety of NiO/AS catalysts demonstrates that industrial waste products may be used in the energy industry for sustainable growth. Physical characteristics like BET surface area and porosity of the catalyst do not have a significant impact, according to the physicochemical analysis of the prepared catalysts, but NiO percentages of dispersion and chemical characteristics like reducibility and basicity are crucial for catalysts to function effectively as catalysts. better NiO dispersion and basicity lead to better reactant conversion because active areas on the catalyst surface are more accessible. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. As a result of all of these good features, 15%NiO/AS exhibits excellent catalytic activity with the reactant.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was funded by a grant from Skim Penyelidikan Lantikan Baru, Universiti Malaysia Sabah (SLB 2252).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConceptualization and writing\u0026mdash;original draft: Mohd Razali Shamsuddin. Data collection, formal analysis, and investigation: Mohd Razali Shamsuddin. Writing\u0026mdash;review and editing: Mohd Razali Shamsuddin, Teo Siow Hwa, Tengku Sharifah Marliza Tengku Azmi, Azizul Hakim Lahuri, Taufiq-Yap Yun Hin Resources and supervision: Taufiq-Yap Yun Hin. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThis research was funded by a grant from Skim Penyelidikan Lantikan Baru, Universiti Malaysia Sabah (SLB 2252).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e Not applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnaya K, Olufemi Oni A, Kumar A (2023) Investigating the techno-economic and environmental performance of chemical looping technology for hydrogen production. 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Mater Chem Phys 57:23\u0026ndash;32. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/S0254-0584(98)00187-4\u003c/span\u003e\u003cspan address=\"10.1016/S0254-0584(98)00187-4\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Nickel, alkaline sludge, dry reforming, methane, carbon dioxide, hydrogen","lastPublishedDoi":"10.21203/rs.3.rs-3869773/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3869773/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAlkali sludge (AS) is abundantly waste generated from solar PV solar cell industries. Since this potential basic material is still underutilized, a combination with NiO catalyst might greatly influence coke resentence, especially in high-temperature thermochemical reactions (Arora and Prasad \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). This paper investigated alkaline sludge containing 3CaO-2SiO\u003csub\u003e2\u003c/sub\u003e doped with well-known NiO to enhance the dry reforming of methane (DRM) reaction. The wet-impregnation method was carried out to prepare the xNiO/AS (x\u0026thinsp;=\u0026thinsp;5\u0026ndash;15%) catalysts and tested them to determine their physicochemical properties. The catalytic performance of xNiO/AS catalysts was investigated in a fixed bed reactor/GC-TCD at a CH\u003csub\u003e4\u003c/sub\u003e: CO\u003csub\u003e2\u003c/sub\u003e flow rate of 30 ml\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e during a 10h reaction by following (Shamsuddin et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2021c\u003c/span\u003e). For optimization parameters, the effects of NiO concentration (5, 10, and 15%), reaction temperature (700, 750, 800, 850, and 900\u0026deg;C), catalyst loading (0.1, 0.2, 0.3, 0.4, and 0.5g), and GHSV (3000, 6000, 9000, 12000, and 15000h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) were evaluated. The results showed that while physical characteristics such as BET surface area and porosity do not significantly impact NiO percentages of dispersion and chemical characteristics like reducibility are crucial for the catalysts' efficient catalytic activity. Due to the active sites on the catalyst surface being more accessible, increased NiO dispersion results in higher reactant conversion. The catalytic performance on various parameters shows 15%NiO/AS exhibits high reactant conversion up to 98% and 40\u0026ndash;60% product selectivity in 700\u003csup\u003eo\u003c/sup\u003eC, 0.2g catalyst loading, and 12000h\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e GHSV (see Fig.\u0026nbsp;1). According to spent catalyst analyses, the catalyst is stable even after the DRM reaction. Meanwhile, increased reducibility resulted in more and better active site formation on the catalyst. Synergetic effect of efficient NiO as active metal and medium basic sites from AS enhanced DRM catalytic activity and stability with low coke formation.\u003c/p\u003e","manuscriptTitle":"Performance of NiO Doped on Alkaline Sludge from Waste Photovoltaic Industries for Catalytic Dry Reforming of Methane","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-01 20:59:55","doi":"10.21203/rs.3.rs-3869773/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revision","date":"2024-03-06T22:45:44+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-02-27T07:35:08+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-02-27T07:34:23+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Environmental Science and Pollution Research","date":"2024-02-26T15:57:58+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-02-09T05:05:19+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Science and Pollution Research","date":"2024-02-01T09:49:16+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-science-and-pollution-research","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"espr","sideBox":"Learn more about [Environmental Science and Pollution Research](https://www.springer.com/journal/11356)","snPcode":"11356","submissionUrl":"https://submission.nature.com/new-submission/11356/3","title":"Environmental Science and Pollution Research","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"b8ac8f27-804e-4af2-805f-3b9cb52b89fa","owner":[],"postedDate":"March 1st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2024-05-01T22:34:12+00:00","versionOfRecord":{"articleIdentity":"rs-3869773","link":"https://doi.org/10.1007/s11356-024-33325-7","journal":{"identity":"environmental-science-and-pollution-research","isVorOnly":false,"title":"Environmental Science and Pollution Research"},"publishedOn":"2024-04-18 22:34:12","publishedOnDateReadable":"April 18th, 2024"},"versionCreatedAt":"2024-03-01 20:59:55","video":"","vorDoi":"10.1007/s11356-024-33325-7","vorDoiUrl":"https://doi.org/10.1007/s11356-024-33325-7","workflowStages":[]},"version":"v1","identity":"rs-3869773","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3869773","identity":"rs-3869773","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}